clean-up workers released in September 2013 by the American Journal of Medicine showed the workers were at an increased risk of developing cancer, leukemia and other illnesses. The study concluded that "clean-up workers exposed to the oil spill and dispersant experienced significantly altered blood profiles, liver enzymes, and somatic symptoms." Studies Alabama researchers found that the dispersant killed plankton and disrupted the Gulf of Mexico's food web, noting that it is "like the middle part of the food chain has been taken away". In late 2012, a study from Georgia Tech and Universidad Autonoma de Aguascalientes in Environmental Pollution journal reported that Corexit used during the BP oil spill had increased the toxicity of the oil by up to 52 times. The study looked at the effects of the oil–Corexit combination on rotifers, which form the base of the food chain. Georgia Tech lab professor Terry Snell said, "There is a synergistic interaction between crude oil and the dispersant that makes it more toxic". He said the addition of Corexit to the gulf spill "probably put a big dent in the planktonic food web for some extended period of time, but nobody really made the measurements to figure out the impact." The leader of the study, Roberto Rico-Martinez (UAA), said "Dispersants are pre-approved to help clean up oil spills and are widely used during disasters....but we have a poor understanding of their toxicity. Our study indicates the increase in toxicity may have been greatly underestimated following the Macondo well explosion." Snell commented: "What remains to be determined is whether the benefits of dispersing the oil by using Corexit are outweighed by the substantial increase in toxicity of the mixture...Perhaps we should allow the oil to naturally disperse. It might take longer, but it would have less toxic impact on marine ecosystems." On their own, oil and Corexit were found to be equally toxic. A study released by Florida State University and Utrecht University, Netherlands in November 2012, found Corexit made oil sink faster and more deeply into the beaches, and possibly groundwater supplies. The researchers found that Corexit 9500A allowed the toxic components of crude oil (PAHs) to permeate sand where, due to a lack of sunlight, degradation is slowed. The authors explained, "The causes of the reduced PAH retention after dispersant application has several reasons: 1) the dispersant transforms the oil containing the PAHs into small micelles that can